Among P, Q, R and S, the aromatic compound(s) is(are)

The total number of carboxylic acid groups is the product P is _________.

EDTA^4$$-$$ is ethylenediaminetetraacetate ion. The total number of N$$-$$Co$$-$$O bond angles in [Co(EDTA)]^1$$-$$ complex ion is ________.

A tetrapeptide has $$-$$COOH group on alanine. This produces glycine (Gly), valine (Val), phenyl alanine (Phe) and alanine (Ala), on complete hydrolysis. For this tetrapeptide, the number of possible sequences (primary structures) with $$-$$NH₂ group attached to a chiral center is _______.